Membrane switch

A membrane switch in which an upper membrane sheet and a lower membrane sheet are laminated with each other through a spacer sheet having therein a bore and forming adhesive material layers on an upper and a lower face thereof, respectively, comprising:

• a switch storing chamber, provided in the bore of the spacer sheet, for storing a pair of opposed electrodes printed on the upper membrane sheet and the lower membrane sheet, respectively, said switch storing chamber being enclosed, except for a gas permeable passage for communicating the switch storing chamber with the exterior, by the adhesive material layers so that the switch chamber is isolated from the exterior;
• at least one upper gas permeable chamber formed between the upper membrane sheet and the spacer sheet by surrounding a peripheral portion of the upper gas permeable chamber by the adhesive material layer, and at least one lower gas permeable chamber formed between the lower membrane sheet and the spacer sheet by surrounding a peripheral portion of the lower gas permeable chamber by the adhesive material layer;
• and
• the at least one upper gas permeable chamber and the at least one lower gas permeable chamber partially overlapping with each other in a vertical direction of the membrane switch, said upper and lower permeable chambers communicating through a gas permeable hole provided in the spacer sheet at an overlapping position of the upper gas permeable chamber and the lower gas permeable chamber, said upper and lower gas permeable chambers and said gas permeable hole forming a gas permeable passage vertically curved in a zigzag shape, wherein
• one side of the gas permeable passage communicates with the exterior and another side of the gas permeable passage communicates with the switch storing chamber.